Move download filename determintion into a separate class.

chrome/browser/download/download_crx_util.cc

 // Copyright (c) 2012 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 //
 // Download code which handles CRX files (extensions, themes, apps, ...).
 
 #include "chrome/browser/download/download_crx_util.h"
 
 #include "chrome/browser/extensions/crx_installer.h"
 #include "chrome/browser/extensions/extension_install_prompt.h"
@@ skipping 107 matching lines @@
   if (download_item.GetMimeType() == extensions::Extension::kMimeType ||
       extensions::UserScript::IsURLUserScript(download_item.GetURL(),
                                               download_item.GetMimeType())) {
     return true;
   } else {
     return false;
   }
 }
 
 bool OffStoreInstallAllowedByPrefs(Profile* profile, const DownloadItem& item) {
-  extensions::ExtensionPrefs* prefs = extensions::ExtensionSystem::Get(
-      profile)->extension_service()->extension_prefs();
+  ExtensionService* service = extensions::ExtensionSystem::Get(
+      profile)->extension_service();
+  if (!service)
+    return false;
+
+  extensions::ExtensionPrefs* prefs = service->extension_prefs();
   CHECK(prefs);
 
   extensions::URLPatternSet url_patterns = prefs->GetAllowedInstallSites();
 
   if (!url_patterns.MatchesURL(item.GetURL()))
     return false;
 
   // The referrer URL must also be whitelisted, unless the URL has the file
   // scheme (there's no referrer for those URLs).
   // TODO(aa): RefererURL is cleared in some cases, for example when going
   // between secure and non-secure URLs. It would be better if DownloadItem
   // tracked the initiating page explicitly.
   return url_patterns.MatchesURL(item.GetReferrerUrl()) ||
          item.GetURL().SchemeIsFile();
 }
 
 }  // namespace download_crx_util